Endocrine hypertension

Question 1

Describe the blood supply to the adrenal glands.

Answer 1

1. Arterial:
   - superior suprarenal artery (branch of inferior phrenic artery)
   - middle suprarenal artery (direct branch of abdominal aorta)
   - inferior suprarenal artery (branch of renal artery)
2. Venous:
   - right suprarenal vein drains into IVC
   - left suprarenal veins drains into the left renal vein/left inferior phrenic vein

Question 2

How should endocrine hypertension be investigated?

Answer 2

1. initial investigations (for all patients with HTN):
   - ECG (signs of MI or LVH?)
   - CXR (cardiomegaly, widening of the left subclavian border?)
   - U&Es, creatinine, random blood glucose and serum cholesterol
   - urine dip
2. subsequent investigations (if clinical suspicion is high):
   - Plasma renin and aldosterone levels (ratio >2 suggests an aldosterone-secreting tumour)
   - Plasma renin activity (elevated in most patients with renal artery stenosis)
   - Late-night salivary cortisol (elevated in Cushing’s syndrome) → can be confirmed with an overnight dexamethasone suppression test)
   - LFTs (chronic alcohol excess + liver dysfunction)
   - TFTs (hyper/hypothyroidism)
   - Serum calcium (hyperparathyroidism)
   - 24h urine collection (catecholamines to exclude a phaeochromocytoma; protein levels in suspected pre-eclampsia or nephrotic syndrome)
   - USS of kidneys and adrenal glands
   - CT of adrenals (to localise phaeochromocytoma if suspected)
   - MRI

Question 3

What is Conn’s syndrome?

Answer 3

• adrenal adenoma
• cause of primary hyperaldosteronism (accounts for >80% of all cases)
• adenomas are usually unilateral and solitary

Question 4

What medications must be stopped before Conn’s syndrome can be properly investigated?

Answer 4

1. Diuretics (4 weeks prior)
2. B-Blockers + dihydropyridine CCBs (at least 2 weeks prior)
3. Steroids
4. Potassium supplements
5. Laxatives

Question 5

What investigations are carried out to diagnose Conn’s syndrome?

Answer 5

1. U&Es: may show hypokalaemia and hypernatraemia
2. Spot renin + aldosterone levels: aldosterone raised + renin low
3. ECG: may show arrhythmias (due to electrolyte imbalance)
4. CT/MRI: adrenal adenoma, adrenal hyperplasia
5. Selective adrenal venous sampling → GOLD STANDARD
6. Genetic testing (familial hyperaldosteronism)
7. Lying and standing aldosterone/rening levels: no alteration in renin/aldosterone with adrenal adenoma → aldosterone would change in normal subjects
8. Salt loading and aldosterone/rening levels: failure to suppress plasma aldosterone confirms primary hyperaldosteronism

Question 6

What is a phaeochromocytoma?

Answer 6

• rare tumour that secretes catecholamines
• derived from chromaffin cells
• usually in adrenal medulla (extra-adrenal phaeochromocytomas or paragangliomas can occur)

Question 7

What investigations are carried out to diagnose a phaeochromocytoma?

Answer 7

1. Blood glucose: elevated
2. Calcium: may be elevated
3. Hb: elevated (due to haemoconcentration from reduction in circulating volume)
4. Plasma catecholamines and plasma metanephrines (plasma free metanephrines = blood test of choice)
5. 24h urine collection for creatinine, total catecholamines, vanillylmandelic acid and metanephrines
6. CT (initial imaging modality of choice): detects ~85-95% of tumours >1cm in diameter
7. MRI: useful for locating metastatic disease
8. Genetic testing
9. Histology (PASS system): PASS score <4 = benign phaemochromocytoma; socre >6 = malignant tumour

Question 8

How can Conn’s syndrome cause endocrine-mediated hypertension?

Answer 8

• excessive aldosterone levels act at the distal renal tubule, promoting sodium retentin
• this results in water retention and volume expansion with hypertension
• also excretion of potassium, resulting in hypokalaemia

Question 9

How can a phaeochromocytoma cause endocrine-mediated hypertension?

Answer 9

• tumour hypersecretion of catecholamines and increased stimulation of alpha and beta adrenergic receptors
• increased stimulation of these adrenergic receptors results in increased peripheral vasoconstriction
• result = hypertension

Question 10

How can renal artery stenosis cause endocrine-mediated hypertension?

Answer 10

• narrowing of the arteries supplying the kidneys
• causes low perfusion pressure that is detected by the juxtaglomerular apparatus
• this leads to rening secretion that causes the angiotensinogen conversion to angiotensin I
• angiotensin I then proceeds to lung where it is converted to angiotensin II via angiotensin converting enzyme

Question 11

Describe the clinical presentation of Conn’s syndrome.

Answer 11

1. Classic features:
   - hypertension
   - hypokalaemia (usually <3.5 mmol/L)
   - metabolic alkalosis
   - sodium normal/high end of normal
2. Potential features:
   - polyuria and polydipsia (reduced ability of kidneys to concentrate urine)
   - weakness (hypokalaemia)
   - headaches + lethargy

Question 12

Describe the clinical presentation of a phaeochromocytoma.

Answer 12

1. Symptoms (intermittent and may vary from once a month to several times a day):
   - headahces
   - profuse sweating
   - palpitations
   - tremor
   - nausea
   - weakness
   - anxiety
   - sense of doom
   - epigastric pain
   - flank pain
   - constipation
   - weight loss
   - asymptomatic (familial phaeochromocytoma)
2. Signs:
   - hypertension
   - postural hypotension
   - tremor
   - hypertensive retinopathy
   - pallor
   - fever
   - reflex bradycardia